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Vortex Flow Phenomena and Physics of Aerospace Engineering Applications

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A special issue of Aerospace (ISSN 2226-4310). This special issue belongs to the section "Aeronautics".

Deadline for manuscript submissions: closed (31 December 2024) | Viewed by 24569

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Special Issue Editors

Dr. Tze How New

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Guest Editor

School of Mechanical & Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore
Interests: vortex dynamics; flow mechanisms; vortex rings; impinging jets; jet mixing enhancements; flow control
Special Issues, Collections and Topics in MDPI journals

Dr. Desmond H. Lim

E-Mail Website
Co-Guest Editor

Centre For Aerodynamics & Propulsion, National University of Singapore, 21 Lower Kent Ridge Rd, Singapore 119077, Singapore
Interests: scalar dispersion; turbulent mixing; air pollution; ventilation; boundary layer; schlieren velocimetry; quantitative schlieren; flow control; jets
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Dr. Nick Zang

E-Mail Website
Co-Guest Editor

School of Engineering and Material Science, Queen Mary University of London, London E1 4NS, UK
Interests: aerodynamics; fluid–structure interactions; aeroacoustics; passive flow and noise control; jet and turbulent mixing; advanced measurement techniques
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Understanding flow fields and their impact upon the aerodynamics of aerial vehicles often demands a good appreciation of the vortex dynamics and flow physics associated with the key flow phenomena that enable and enhance the functionalities of said aerial vehicles. Therefore, this Special Issue includes but is not limited to conventional fixed-wing or rotary-wing aircraft, unmanned aerial vehicles, launch vehicles, bio-inspired solutions and projectile flights, just to mention a few applications. While parametric pursuits are often undertaken numerically or experimentally to improve and optimize their designs, the role played by exploiting and optimizing the underlying fundamental flow mechanisms cannot be underestimated as well. In fact, the latter is a more of an upstream approach that could arguably lead to more efficient and effective solutions and/or concepts as it tackles at the heart of the problem. Having said that, unravelling the vortex dynamics and flow physics of many aerospace engineering applications is often challenging, especially when a myriad of different flow phenomena co-exist under unsteady, high-speed or turbulent flow conditions. This Special Issue calls upon researchers who are addressing these challenges to submit their findings in order to better disseminate knowledge with the aim of informing the research community about their progress; indeed, a more collective understanding can help the community to advance significantly.

Dr. Tze How New
Dr. Desmond H. Lim
Dr. Nick Zang
Guest Editors

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Keywords

aerodynamics
fluid dynamics
vortex dynamics
flow mechanism
flow physics
boundary layer
flow separation
viscous flow
flow transitions
flow instabilities

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Related Special Issue

Vortex Flow Phenomena and Physics of Aerospace Engineering Applications (2nd Edition) in Aerospace

Published Papers (10 papers)

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Research

Jump to: Review

24 pages, 4216 KiB

Open AccessArticle

Improvement of a Free-Wake Model for the Aerodynamic and Aeroacoustic Analysis of a Small-Scale Two-Bladed Propeller in Hover

by Manuel Iannotta, Antonio Visingardi, Domenico Quagliarella, Fabrizio De Gregorio, Mattia Barbarino and Alex Zanotti

Aerospace 2025, 12(1), 5; https://doi.org/10.3390/aerospace12010005 - 25 Dec 2024

Cited by 1 | Viewed by 909

Abstract

The aim of the present work is the improvement of a free-wake model for the analysis of a small-scale two-bladed propeller in hover. The simulations are carried out using a BEM approach implemented in the medium-fidelity solver RAMSYS. An acoustic validation is also performed using the developed tool ACO-FWH. The work proves that even mild discrepancies in the propeller geometry must be accounted for as their influence is not negligible, especially on the aeroacoustics of the propeller. In particular, the proper modeling of the blades enables the correct identification of the sub-harmonics of the SPL spectra. An optimization procedure based on the application of the evolutionary Genetic Algorithm is followed to identify the values of the parameters describing the dissipative and diffusive properties in the Bhagwat–Leishman vortex core model, an upgraded version of the classical Lamb–Oseen one. On average, this approach enabled the further improvement of the accuracy of the numerical model in terms of acoustic signature evaluation with respect to the one obtained by only modeling blade dissimilarities. The results obtained demonstrate the promising capabilities of a fine-tuned free-wake medium-fidelity approach to simulate the aerodynamic and acoustic details of a small-scale propeller in hover, provided the accurate geometrical modeling of the propeller and the selection of suitable parameters to be used in the wake modeling. Full article

(This article belongs to the Special Issue Vortex Flow Phenomena and Physics of Aerospace Engineering Applications)

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18 pages, 6867 KiB

Open AccessArticle

Study on the Influence of Different Slot Sizes on the Flow Field of Transonic Compressor Rotors

by Yu Gao, Xiaodong Li and Jingjun Zhong

Aerospace 2024, 11(10), 825; https://doi.org/10.3390/aerospace11100825 - 8 Oct 2024

Viewed by 887

Abstract

Blade slotting technology is an effective measure to improve the flow structure on the suction surface of a blade and enhance the performance of turbomachinery. To investigate the impact of various slot sizes on the flow field of a single-stage transonic compressor rotor, seven kinds of slot schemes were designed and calculated by numerical simulations. The results show that the above slotting schemes significantly enhance the stability margin of the compressor. In particular, the slotting scheme H9W3 increases the surge margin by 60.9% and slightly reduces peak efficiency by 0.3%, with an almost identical maximum pressure ratio. Slotting promotes high-energy fluid to generate jets from the slot located at the exit of the suction side, effectively controlling blade surface flow separation and reducing channel blockage. Square slots are more effective than elongated slots for controlling separation when using differently shaped slots with equal areas. Increasing slot area gradually decreases outlet total pressure at a constant aspect ratio. A slight increase in the overall blade load causes a backward shift in the front portion load. Full article

(This article belongs to the Special Issue Vortex Flow Phenomena and Physics of Aerospace Engineering Applications)

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20 pages, 22717 KiB

Open AccessArticle

Görtler Vortices in the Shock Wave/Boundary-Layer Interaction Induced by Curved Swept Compression Ramp

by Liang Chen, Yue Zhang, Juanjuan Wang, Hongchao Xue, Yixuan Xu, Ziyun Wang and Huijun Tan

Aerospace 2024, 11(9), 760; https://doi.org/10.3390/aerospace11090760 - 17 Sep 2024

Viewed by 1013

Abstract

This study builds on previous research into the basic flow structure of a separated curved swept compression ramp shock wave/turbulence boundary layer interaction (CSCR-SWBLI) at the leading edge of an inward-turning inlet. We employ the ice-cluster-based planar laser scattering (IC-PLS) technique, which integrates multiple observation directions and positions, to experimentally investigate a physical model with typical parameter states at a freestream Mach number of 2.85. This study captures the fine structure of some sections of the flow field and identifies the presence of Görtler vortices (GVs) in the CSCR-SWBLI. It is observed that due to the characteristics of variable sweep angle, variable intensity interaction, and centrifugal force, GVs exhibit strong three-dimensional characteristics in the curved section. Additionally, their position is not fixed in the spanwise direction, demonstrating strong intermittence. As the vortices develop downstream, their size gradually increases while the number decreases, always corresponding to the local boundary layer thickness. When considering the effects of coupling of bilateral walls, it is noted that the main difference between double-sided coupling and single-sided uncoupling conditions is the presence of a large-scale vortex in the central plane and an odd number of GVs in the double-sided model. Finally, the existence of GVs in CSCR-SWBLI is verified through the classical determine criteria Görtler number (G_T) and Floryan number (F) decision basis. Full article

(This article belongs to the Special Issue Vortex Flow Phenomena and Physics of Aerospace Engineering Applications)

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11 pages, 4834 KiB

Open AccessArticle

Analysis of Bubble Flow in an Inclined Tube and Modeling of Flow Prediction

by Xiaodi Liang, Suofang Wang and Wenjie Shen

Aerospace 2024, 11(8), 655; https://doi.org/10.3390/aerospace11080655 - 11 Aug 2024

Cited by 1 | Viewed by 1063

Abstract

The lubricating oil system is a significant component of aviation engine lubrication and cooling, and the scavenge pipe is an essential component of the lubricating oil system. Accurately identifying and understanding the flow state of the scavenge pipe is very important. This article establishes a visualization test bench for a 45-degree inclined scavenge pipe, with upward and downward flow directions, respectively. The test temperature is 370 K, and a high-speed camera captures the changes in the two-phase flow inside the pipeline. Based on high-speed photography photos, we develop software for analyzing the flow characteristics of bubbles inside the tube and explore the influence of gas phase conversion velocity and liquid phase conversion velocity on the apparent velocity of bubbles inside the tube. Multiple algorithms were used to develop the model by combining machine learning with speed and accuracy to establish a data regression prediction model for the apparent velocity of bubbles inside the tube. Through calculation and analysis, it was found that the root mean square error of the prediction model using the BP neural network algorithm was the lowest, and the decision coefficient of the prediction model using the support vector machine algorithm was the highest. Full article

(This article belongs to the Special Issue Vortex Flow Phenomena and Physics of Aerospace Engineering Applications)

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51 pages, 6383 KiB

Open AccessArticle

Aerodynamic Instabilities in High-Speed Air Intakes and Their Role in Propulsion System Integration

by Aristia L. Philippou, Pavlos K. Zachos and David G. MacManus

Aerospace 2024, 11(1), 75; https://doi.org/10.3390/aerospace11010075 - 12 Jan 2024

Cited by 3 | Viewed by 6011

Abstract

High-speed air intakes often exhibit intricate flow patterns, with a specific type of flow instability known as ‘buzz’, characterized by unsteady shock oscillations at the inlet. This paper presents a comprehensive review of prior research, focused on unraveling the mechanisms that trigger buzz and its implications for engine stability and performance. The literature survey delves into studies concerning complex-shaped diffusers and isolators, offering a thorough examination of flow aerodynamics in unstable environments. Furthermore, this paper provides an overview of contemporary techniques for mitigating flow instability through both active and passive flow control methods. These techniques encompass boundary layer bleeding, the application of vortex generators, and strategies involving mass injection and energy deposition. The study concludes by discussing future prospects in the domain of engine-intake aerodynamic compatibility. This work serves as a valuable resource for researchers and engineers striving to address and understand the complexities of high-speed air induction systems. Full article

(This article belongs to the Special Issue Vortex Flow Phenomena and Physics of Aerospace Engineering Applications)

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15 pages, 7934 KiB

Open AccessCommunication

Simulations of Compression Ramp Shock Wave/Turbulent Boundary Layer Interaction Controlled via Steady Jets at High Reynolds Number

by Tingkai Dai and Bo Zhang

Aerospace 2023, 10(10), 892; https://doi.org/10.3390/aerospace10100892 - 19 Oct 2023

Viewed by 2021

Abstract

Shock wave/turbulent boundary layer interaction (SBLI) is one of the most common physical phenomena in transonic wing and supersonic aircraft. In this study, the compression ramp SBLI (CR-SBLI) was simulated at a 24° corner at Mach 2.84 using the open-source OpenFOAM improved delayed [...] Read more.

1.57 \times 10^{6}

. The results of the control effect of the jet vortex generator on CR-SBLI showed that the jet array can effectively reduce the length of the separation zone. The simulation results of different jet parameters are obtained. With the increasing jet angle, the reduction in the length of the separation zone first increased and then decreased. In this work, when the jet angle was 60°, the location of the separation point was

x / δ = - 1.48

, which was smaller than other jet angles. The different distances of the jet array also had a great influence. When the distance between the jet and the corner

d_{j e t} = 70 m m

, the location of the separation point

x / δ = - 1.48

was smaller than that when

d_{j e t} = 65 / 60 m m

. A closer distance between the jet hole and the corner caused the vortex structures to squeeze each other, preventing the formation of a complete vortex structure. On the other hand, when the jet was farther away, the vortex structures could separate effectively before reaching the shock wave, resulting in a better inhibition of SBLI. The simulation primarily focused on exploring the effects of the jet angle and distance, and we obtained the jet parameters that provided the best control effect, effectively reducing the length of the CR-SBLI separation zone. Full article

(This article belongs to the Special Issue Vortex Flow Phenomena and Physics of Aerospace Engineering Applications)

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20 pages, 35978 KiB

Open AccessArticle

Investigation of the Influence of Wake Field Characteristic Structures on Downstream Targets Using the POD Method

by Jiawei Fu, Junhui Wang, Jifei Wu, Ke Xu and Shuling Tian

Aerospace 2023, 10(9), 824; https://doi.org/10.3390/aerospace10090824 - 21 Sep 2023

Cited by 1 | Viewed by 1537

Abstract

This research investigated the impact of complex low-speed wake flow structures on the aerodynamic characteristics of objects downstream. It employed the proper orthogonal decomposition (POD) method and the domain precursor simulation method to compare traditional methods and validate this approach. The study generated several flow structures of parallel dual-cylinder wakes with different scales and spacing. The variations in the aerodynamic coefficient of three downstream objects at various times passing through wakes of varying scales were appropriately compared and analyzed. The study established that the wake with a cylinder spacing of G = 1.5 has a more compact and concentrated modal structure than that with a cylinder spacing of G = 0.35. Smaller objects were more responsive to the wake flow structure with a spacing of G = 1.5, whereas larger objects responded more to the flow structure with a spacing of G = 0.35. The achieved results also revealed that the aerodynamic force coefficients of objects passing through the wakefield at different times were closely related to the temporal characteristics of the wake flow structure with different scales. Full article

(This article belongs to the Special Issue Vortex Flow Phenomena and Physics of Aerospace Engineering Applications)

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19 pages, 14254 KiB

Open AccessArticle

Study of Circumferential Grooved Casing Treatment on Cascade Aerodynamic Performance

by Jingbo Tan, Chun Zhang, Huiling Zhu, Ling Zhou and Lucheng Ji

Aerospace 2023, 10(8), 666; https://doi.org/10.3390/aerospace10080666 - 27 Jul 2023

Cited by 2 | Viewed by 1508

Abstract

To explore the influence of circumferential grooved casing treatment on subsonic cascade performance, a numerical simulation of subsonic cascade was conducted. In contrast to traditional research on variable single parameters for casing treatment, this paper used the Latin hypercube sampling method to randomly sample multiple geometric parameters of casing treatment and compared many sample data with the total pressure loss of the cascade as a measurement standard. After selecting several typical cases of high and low total pressure loss cases for in-depth flow field analysis, it was found that casing treatment affects the strength and structure of the leakage vortex, thereby reducing the blockage of fluid in the passage of the cascade. Changes in the total pressure loss and in the margin of the cascade meant that casing treatment affected cascade performance. This prompted analysis of the correlation between the casing treatment parameters and total pressure loss of the cascade. The clearance height and groove depth had the greatest influence on the total pressure loss of the cascade. Full article

(This article belongs to the Special Issue Vortex Flow Phenomena and Physics of Aerospace Engineering Applications)

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19 pages, 22389 KiB

Open AccessArticle

Flow Structures and Aerodynamic Behavior of a Small-Scale Joined-Wing Aerial Vehicle under Subsonic Conditions

by Tze How New, Zhen Wei Teo, S. Li, Z. A. Ong and Björn Nagel

Aerospace 2023, 10(8), 661; https://doi.org/10.3390/aerospace10080661 - 25 Jul 2023

Cited by 2 | Viewed by 2373

Abstract

Flow behavior and aerodynamic performance of a small-scale joined-wing unmanned aerial vehicle (UAV) was studied experimentally and numerically under various pitch and yaw angle combinations in subsonic flow conditions. Selected numerical results are compared against experimental results obtained using surface oil flow visualizations and force measurements, with additional simulations expanding the range of combined pitch and yaw configurations. Under zero-yaw conditions, increasing the pitch angle leads to the formation of symmetric ogive vortex roll-ups close to the fuselage and their significant interactions with the fore-wing. Additionally, contributions to lift and drag coefficients under zero-yaw conditions by the key UAV components have been documented in detail. In contrast, when the UAV is subjected to combined pitch and yaw, no clear evidence of such ogive vortex roll-ups can be observed. Instead, asymmetric flow separations occur over the fuselage’s port side and resemble bluff-body flow behavior. Additionally, these flow separations become more complex, and they interact more with the fuselage and fore- and aft-wings when the yaw angle increases. Lift and drag variations due to different pitch and yaw angle combinations are also documented. Finally, rolling and yawing moment results suggest that the present UAV possesses adequate flight stability unless the pitch and yaw angles are high. Full article

(This article belongs to the Special Issue Vortex Flow Phenomena and Physics of Aerospace Engineering Applications)

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Review

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26 pages, 18830 KiB

Open AccessReview

Developments in Wingtip Vorticity Mitigation Techniques: A Comprehensive Review

by Yousef Gharbia, Javad Farrokhi Derakhshandeh, Md. Mahbub Alam and A. M. Amer

Aerospace 2024, 11(1), 36; https://doi.org/10.3390/aerospace11010036 - 29 Dec 2023

Cited by 7 | Viewed by 5813

Abstract

Wingtip vortices generated from aircraft wingtips, as a result of the pressure differential at the wingtip, constitute a major component of the total drag force, especially during take-off and landing. In addition to the drag issue, these vortices also pose a significant hazard to smaller aircraft flying in the wake of the larger airplane. The wingtip vortices play a crucial role in aerodynamic efficiency, fuel consumption, flight range, and aircraft stability. This paper presents an overview of the volume of work conducted over the past six decades to encapsulate the phenomena and the techniques devised to mitigate the wingtip vortices. It is shown that the aerodynamic efficiency of the examined wingtip devices ranges from 1% to 15%, depending on the type of wingtips and the flight conditions. Furthermore, it is pointed out that the decrease in fuel consumption ranges from 3.4% to 10%, and the reduction in the induced drag ranges from 5% to 20%. Full article

(This article belongs to the Special Issue Vortex Flow Phenomena and Physics of Aerospace Engineering Applications)

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